People are already sharing lots of photos in Messenger, and Facebook already knows what your friends look like.

Last month, 9.5 billion photos were sent within Messenger. People like to use it for photo sharing, and Facebook wants to encourage that. So the company is applying its facial recognition technology directly to your camera roll so it can scan the pictures you haven't uploaded yet. When it sees a Facebook friend in one, Facebook will suggest you send it to them through its Messenger app. Here's how it will work.

Facebook won't scan your camera roll at all times.

But it might do so frequently, if you decide to use Photo Magic. On Android, Messenger will be alerted every time a new photo is taken. On iOS, it will check in periodically. It will only scan for new photos.